Currently available immunomodulatory therapies do not modulate the pathogenesis of axonal degeneration once it is established and are only partially effective in preventing the onset of permanent disability in MS patients. Identifying a drug that stimulates endogenous myelination and spares axon degeneration would theoretically reduce the rate of disease progression. We have previously shown that treatment of demyelinating mouse models with estrogen receptor (ER)? ligand, diarylpropionitrile (DPN) has the potential for fulfilling this role. Because DPN is a generic ER? ligand with low specificity we are screening higher specificity ER? ligands that are available to the PI through collaborations and material transfer agreements. We propose to examine here, the stimulation of remyelination and the signal transduction pathway activated by the therapeutic effects of commercially available and chemist generated specific ER? ligands in two different demyelinating mouse models of MS. The central hypothesis of the proposed experiments is that therapeutic treatment with ER? ligand will cause activation of the IFG1/Akt/mTOR signaling pathway to induce OL survival and endogenous myelination in mouse models of demyelination. This hypothesis will be tested by pursuing two specific aims: The first aim will determine which ER? ligands induce the most robust remyelination and neuroprotection during therapeutic treatment in mouse models of MS. EAE and CPZ will be therapeutically treated with different commercially available and new ER? ligands. The two most effective ER? ligands will be analyzed further for their mechanism of action. The second aim will determine if treatment with different ER? ligands regulate signaling molecules that affect OL survival and differentiation. Under the first specific aim behavioral (clinical scores and rotarod), immunological (cytokines), demyelination and axonal integrity (electrophysiology, immunohistochemistry, electron microscopy) will be assessed. Under the second specific aim dissected corpus callosum, fluorescence activated and antibody-conjugated microbead sorted OLs from various EAE treatment groups for gene and protein analysis. To verify the effects of ER? ligand on specifically OLP/OL cells in vivo and gain insight into our mechanistic understanding of how ER? ligands exert its promyelinating influence during disease, we will use ER? conditional knock-out mice targeted to OLP/OL cells. In summary, once the aims of our project are achieved, we will not only reveal the best available ER? ligands, but also reveal their mechanism of action. In addition, exploring OL survival and differentiation related gene and protein analysis along with use of ER? ligand conditional knock-out mice in OLs allows us to conclude a direct or indirect effect of the drugs. As a neuroprotective agent that enhances myelination, such ER?-targeted agents could be given in combination with the currently available anti-inflammatory agents.